As integrated circuits have been able to have more and more transistors, a continuing trend has been to have more and more functions on a particular integrated circuit. This has been generally called a system on a chip (SOC). A common characteristic of SOC type integrated circuits is one or more processors coupled to a variety of functional circuits through different interface buses. With the functional circuits on the integrated circuit, it is often more efficient to design the integrated circuit in such a way that results in not having access to the internal buses from outside the integrated circuit. Without access to the internal buses, it can be difficult to debug the integrated circuit during qualification of the product.
To help this, trace buffers have been developed to provide certain internal bus information under certain conditions. This has been helpful but the information has been limited and certainly less complete than having direct access to the internal bus.
Thus, there is a need to have better information about the bus in a SOC type integrated circuit.